1. Field of the Invention
The present invention relates to elastic wave devices and manufacturing methods for the same.
2. Description of the Related Art
Various types of elastic wave devices using plate waves have been proposed. An elastic wave device making use of plate waves and including a hollow section is disclosed in Japanese Unexamined Patent Application Publication No. 2014-13991 and WO 2012/073871 A1. In Japanese Unexamined Patent Application Publication No. 2014-13991, at a time of forming a hollow section, a sacrificial layer is formed in advance. A piezoelectric thin film is laminated on the sacrificial layer. A through-hole for etching is formed in the piezoelectric thin film. Then, performing etching through the through-hole for etching removes the sacrificial layer, thus forming the hollow section. Also in WO 2012/073871 A1, a similar through-hole for etching is provided in a region in an outer side portion of a reflector.
In the case where a through-hole for etching is provided as described in Japanese Unexamined Patent Application Publication No. 2014-13991 and WO 2012/073871 A1, an area of the piezoelectric thin film becomes larger accordingly. In addition, an area of the sacrificial layer becomes larger as well. In the case where the areas of the piezoelectric thin film, the sacrificial layer, and the like become large, the size of the elastic wave device including a piezoelectric substrate consequently becomes large. Therefore, in order to miniaturize an elastic wave device, it is required to make the areas of a piezoelectric thin film, a sacrificial layer, and the like be small.